Wavelength Division Multiplexing (“WDM”) is a method of simultaneously transporting data from a plurality of sources over a single fiber optic link. To distinguish the data from the plurality of sources, data from each source travels over the single fiber optic link at a unique wavelength. Thus, WDM provides the ability to carry multiple sets of data over a single fiber optic link, instead of sending each set of data over its own fiber optic link.
Traditional WDM networks comprise a primary fiber optic link and a protection data path between each data source for each desired direction of data flow. Each primary fiber optic link and protection data path may only carry data packets traveling in one direction Thus, for two data sources to have the ability to pass data packets between each other, WDM networks require four fiber optic links. One set of a primary fiber optic link and a protection data path may carry data packets from a first data source to a second data source, and a second set of a primary fiber optic link and a protection data path may carry data packets from the second data source to the first data source.
During normal operation, the data from the plurality of sources travels over the primary fiber optic link. However, if a failure such as a break occurs in the primary fiber optic link, the data from the plurality of sources is routed to the protection data path. For critical applications where loss of the ability to transmit and receive data is absolutely necessary, protection is paramount. Providing a protection data path (for non-critical applications or for other applications which inherently possess the ability to protect data) for every connection between the plurality of sources within the WDM network is costly and inefficient.